Actor joins fight against the Keystone XL pipeline, a route connecting the tar sands in Canada to refineries on the Gulf of Mexico.

When it comes to environmental activism, Mark Ruffalo is quickly building a reputation as a guy you can turn to for support.

The actor recently recorded a PSA in support for Tar Sands Action, an action group fighting to stop the proposed 1,700-mile Keystone XL pipeline between Canada's tar sands and refineries in the Gulf of Mexico. “I’ve seen the kind of damage that out-of-control energy development can do to water and to communities near my own home, where fracking for natural gas is causing widespread pollution," he says in the video. "All these problems are connected — we need to get off fossil fuels.”

Ruffalo, 43, is widely credited with using his celebrity to bring greater awareness to environmental issues. He recently received the prestigious Entertainment Industry Environmental Leadership Award in recognition of his campaign to ban hydrofracking and other green efforts. His own environmental foundation, Water Defense, is also helping to spearhead campaigns promoting clean water and healthy environments, and to encourage clean energy solutions throughout the U.S.

"The root of this is our addiction to carbon-based fuels," he recently told The Hollywood Reporter. "Everywhere we turn, they are touching our lives in a negative way, and our extraction methods are getting more and more desperate because there’s no more easy fuel. As we get more desperate, more of our natural processes will get destroyed in the process."

As Ruffalo explains in the video, Tar Sands Action will be holding peaceful protests outside the White House between Aug. 20 and Sept. 3. Requests for volunteers to join in the event come with the stipulation that participants should expect to stay in D.C. for three days — one for training, one for action, and one (wisely) for any "legal issues."

President Obama, under a bill passed in July by the U.S. House of Representatives, has until Nov. 1 to decide whether or not to approve the $7 billion pipeline. Check out Ruffalo's PSA below.